**3.4 Human occupied vehicle**

HOV is similar to a small submarine; however, a submarine is not submersible. Equipment on an HOV typically includes a manipulator, a camera system, and a special lighting system. HOV is a more versatile underwater vehicle than a submarine, which is reflected in several applications. An HOV is designed to dive to greater depths, just like a submarine. Due to enormous pressures in the deep sea, it requires a special pressure-resistant design that carries no more than two or three people and limited food, water, and oxygen.

According to the database of the Manned Underwater Vehicles Professional Committee of the Marine Technology Society (MTS) of the United States, there are currently 16 HOVs worldwide with a depth capacity of over 1000 m [12]. These include the Alvin (4500 m; United States), Nautile (6000 m; France), Mir I and Mir II (6000 m; Russia), Shinkai 6500 (6500 m; Japan), and Jiaolong (7000 m; China).

Jiaolong is equipped with a BSSS system to obtain accurate mapping of seafloor topography and geomorphology, similar to other great-depth HOVs, as shown in **Figure 7**. The BSSS system consists of two parts: one part is installed in the manned cabin (i.e., the master controller unit), whereas the other part is installed outside the manned cabin (i.e., the electronic cabin, port-side transducer array, starboardside transducer array, and subsidiary sensors).

The major axis of the BSSS transducer array must be parallel to the major axis of the HOV. The transducer surface normal must have an angle of 30° above the horizontal plane. In addition, the transducer array is installed between HOV stations 4 and 5 as deformation of the mounting bracket must be minimized during lifting to avoid damaging the transducer array. In this cylindrical part of the HOV, the transducer array has a better line-type after installation; the mounting bracket is independent of the load-bearing frame, thereby reducing the impact of frame deformation on the transducers.

BSSS is mainly used to obtain data on micro-topography and micro-geomorphology: ultra-short baseline (USBL) and long baseline (LBL) provide navigation and positioning data, which are essential for topographical and geomorphological mapping; underwater acoustic communication devices transmit positioning data obtained by USBL on the supporting mothership at the surface to HOV, allowing the

**39**

**Figure 8.**

*Advanced Mapping of the Seafloor Using Sea Vehicle Mounted Sounding Technologies*

determination of the initial position of the integrated navigation system; the HOV speed is measured by Doppler velocity log (DVL). The attitude and heading are measured by optical fiber compass. The sound speed is provided by the conductivity-temperature-depth (CTD). The depth of HOV is measured by a high-accuracy depth sensor, which combined with topographical data measured by BSSS, the

In general, factors affecting data quality when using small underwater vehicles (e.g., DT and AUV) to carry near-seafloor micro-topographical mapping sonars fall into five categories: horizontal positioning accuracy, vertical positioning accuracy, depth accuracy, sensor time uniformity (time requirements of the sensor are uniform, the attitude sensor time is accurate to 50 ms, the transmission time is accurate to 50 ms, and the other sensors are accurate to 1 s), and sensor location uniformity (it requires precise knowledge of the coordinates of each sensor relative to the origin of the coordinates origin and installation errors). Large-scale underwater vehicles (e.g., ROV and HOV) not only have the above five features but also have other additional characteristics, including poor stability in attitude control, acoustic transducer array port and starboard installations, and wide spacing. Hence, detailed discussion on factors affecting mapping and detection results is presented using Jiaolong HOV and its BSSS as an example. By processing the BSSS detection data collected by the Jiaolong HOV, we found that factors that mostly affect mapping quality are the HOV

Because the streamline of HOV and manual control, the attitude control stability of HOV is relatively poor; therefore, HOV attitude is a main factor that effect BSSS detection and mapping. **Figure 8** shows the seafloor micro-topography around the peak of a cold spring area. **Figure 8a** uses raw data; **Figure 8b** uses data in which

*Seafloor micro-topography around the peak of a cold spring area: (a) map using raw data and (b) map using* 

*DOI: http://dx.doi.org/10.5772/intechopen.83448*

absolute depth of the seafloor can be obtained.

**4. Factors affecting mapping and detection results**

attitude, port and starboard positions of BSSS transducer array [7].

filtering and smoothing have been applied to the roll angle.

*data in which filtering and smoothing have been applied to the roll angle.*

**4.1 Effect of HOV attitude**

**Figure 7.** *Human-occupied vehicle Jiaolong.*

*Advanced Mapping of the Seafloor Using Sea Vehicle Mounted Sounding Technologies DOI: http://dx.doi.org/10.5772/intechopen.83448*

determination of the initial position of the integrated navigation system; the HOV speed is measured by Doppler velocity log (DVL). The attitude and heading are measured by optical fiber compass. The sound speed is provided by the conductivity-temperature-depth (CTD). The depth of HOV is measured by a high-accuracy depth sensor, which combined with topographical data measured by BSSS, the absolute depth of the seafloor can be obtained.
